Add Results.Stream overload that takes a Func<Stream, Task>

Background and Motivation

There are scenarios where APIs want to work directly on the response stream without buffering. Today the Stream overloads assume you have a stream that you have produced that is then copied to the underlying response stream, instead, we want to provide a result type that gives you access to the underlying response stream.

Example:

https://github.com/khalidabuhakmeh/dotnet-dramameter/blob/main/DramaMeter/Program.cs#L37-L43

Another is writing a blob storage results to the http response.

Proposed API

namespace Microsoft.AspNetCore.Http
{
    public static class Results
    {
+       public IResult Stream(Func<Stream, Task> streamWriterCallback, 
+                             string? contentType = null,
+                             string? fileDownloadName = null,
+                             DateTimeOffset? lastModified = null,
+                             EntityTagHeaderValue? entityTag = null,
+                             bool enableRangeProcessing = false);
    }
}

Usage Examples

app.MapGet("/", async (HttpContext http, string? level) => {
    level ??= "low";

    if (!levels.TryGetValue(level.Trim(), out var result))
        return Results.BadRequest("invalid level");

    var image = background.CloneAs<Rgba32>();
    image.Mutate(ctx => {
        ctx.Vignette(result.color); // match the background to the intensity
        ctx.DrawImage(foreground, new Point(0, 0), 1f);
        ctx.DrawImage(result.image, new Point(0, 0), opacity: 1f);
    });
    
    http.Response.Headers.CacheControl = $"public,max-age={FromHours(24).TotalSeconds}";
    return Results.Stream(stream => image.SaveAsync(stream, PngFormat.Instance), "image/png");
});

Risks

None